By being pasted on the back of a sheet material such as label and transfer paper via an adhesive layer, the prior art stripping paper is primarily intended to protect said adhesive as it is releasably adhered to the adhesive. The stripping paper is coated with a polymer silicone film or special resin film over the entire surface on the side which contacts said adhesive in order to achieve such effect.
As the prior art stripping papers coated with a silicone film, there have been known those having substrates made of densely arranged short fibers such as specially treated kraft paper and super-calendered glacin paper which can prevent a large amount of relatively expensive silicone from infiltrating into the tissue of the paper, and can save the amount of silicone.
As another example of the prior art stripping paper, it is known to laminate a polyethylene film of about 12-14 .mu.m thickness on a sheet of kraft paper to prevent infiltration of silicone into the tissue, to cut down cost and to improve the product quality.
As a stripping paper for adhesive labels is releasably adhered to the label by a stripping layer such as a silicone film and a special film, it is essentially expected to function as a support for the label until the label is peeled off and pasted on an object article, and is therefore made to be easily stripped off from the silicone film or the adhesive on the label. After the label is pasted on an object article, the stripping paper will no longer have its use and is usually discarded and put to incineration.
In an attempt to allow an adequate amount of expensive silicone to be impregnated or to prevent wasteful use of such expensive silicone or high quality paper as the substrate that are often used in a stripping paper, extra treatment such as laminating a polyethylene film is conducted, entailing far greater production cost than is required in the manufacture of ordinary paper products. It is therefore a grave problem in terms of effective utilization of resources that such expensive stripping paper is discarded wastefully after a label to which the stripping paper is bonded is put to use.
Therefore, a means or method of some sort should be developed to make full use of the stripping paper, and there are two conceivable means. For one, left-over stripping paper may be recycled and used as a regenerated paper after an adhesive sheet such as a label is used. Alternatively, a stripping paper which has heretofore been discarded as a blank sheet without being used as a medium for printing may be printed with information to be conveyed to consumers, like the labels.
Recycling of prior art stripping paper for use as regenerated paper is disadvantageous in that it is very difficult to dissolve the recycled stripping paper during regeneration process when compared with other types of paper because glacin paper or kraft paper of relatively short fibers used as substrate is calendered during the manufacturing process to compact the fibers to impart it an adequate strength and to thereby minimize infiltration into the substrate of expensive silicone which is coated on the surface.
Even if the stripping paper comprising a substrate of such quality paper does become dissolved, short fibers easily get washed off during the regeneration process, significantly lowering the fiber recovery ratio and thus the yield of regeneration.
To ensure firm adhesion of silicone layer on the substrate made of compacted short fibers, an intermediate bonding layer of relatively coarse mineral particles having the particle size of about 2.0 .mu.m such as particles of kaolin (:H.sub.2 Al.sub.2 Si.sub.2 O.sub.8 H.sub.2 O) or calcium carbonate (:CaCO.sub.3) is applied on the surface of the substrate, and silicone is applied on this mineral particle layer. Because of relatively large particle size, the resulting interlaminar layer has a sufficient thickness, and when liquid silicone is applied on the surface of this mineral particle layer 2 to form a silicone film layer 3 as shown in FIG. 5, the liquid silicone would infiltrate into the tissue of the substrate 1 through the interstices between the particles and form branches 3a of silicone to bite into the tissue and enhance bonding of the silicone layer 3 with the substrate 1. This biting and bonding of the silicone into and with the substrate fibers makes it more difficult to dissolve the fibers during the regeneration process.
Moreover, a polyethylene film laminated on the surface of the substrate would remain as a foreign matter when the stripping paper is being treated for regeneration. Because of these problems, the prior art stripping paper has been considered totally unsuitable for recycling and regeneration and has therefore been disposed of by incineration.
Use of a stripping paper as a medium for printing is practically impossible as the silicone or polyethylene film is applied on the surface. Although it is possible to print on the surface of the substrate before applying a silicone film layer thereon as far as printing is concerned, the prior art stripping paper is, as described above, provided with a coating layer of relatively large mineral particles to give adequate bonding strength between the silicone film and the substrate which is made of compacted fibers, and the mineral coating layer lacks surface smoothness as the particle size of the mineral is relatively large, and when printed, the resultant printed surface becomes inferior in quality.